Cadmium plating process and composition



the work.

Patented Sept. 26, 1950 OFFICE CADMIUM PLATING PROCESS AND COMPOSITION Richard 0. Hull, Lakewood, Ohio N Drawing. Application November 21, 1945, Serial No. 630,146

9 Claims. (01. 204-40) This invention relates to the electrodeposition of cadmium and more particularly to cyanidecadmium plating compositions, plating baths, and plating processes which employ as an addition agent a sulfonated marine animal oil.

A number of distinct properties are highly important in a commercial cadmium plating process and bath. It is necessary, for instance, that a bright deposit be obtainable over a wide current density range, since in the plating of irregular objects the current density will be different at different points on the objects. It is also necessary for the throwing power to be good, so that the deposits plated out will have relatively uniform thickness on high spots and in recesses of It is also necessary that the deposits be free from streaks and pits, and show good coverage over the entire area plated. Other prime necessities are that the deposits obtainable be smooth, adherent, bright, and of a generally pleasing character and appearance.

Cadmium deposits as normally obtained from cadmium plating solution, including cyanidecadmium solutions, do not possess these desired properties, and it has been proposed to use various addition agents to improve one or another of the characteristics of the deposits. Unfortunately, the addition agents heretofore proposed have often been effective only to improve one particular characteristic of the deposit or of the process and bath, without having an appreciable beneficial effect on the other characteristics, and in some instances the eiiect on other character istics has even been detrimental. For instances, some proposed addition agents give a brilliant deposit, yet are commercially unusable because the current density range of the bath is extremely narrow. Furthermore, many of the more effective addition agents proposed are so expensive that their commercial adoption has been impeded.

Now according to the present invention it has been found that smooth, adherent, and bright deposits of cadmium free of pits and streaks and having a pleasing appearance can be produced with good throwing power and over a wide range of current densities by cyanide-cadmium plating compositions, plating baths, and plating processes which employ as an addition agent a sulfonated marine animal oil.

Marine animal oils are widely available at relatively low cost, and consequently the deposits of improved character can be produced at less expense than has attended the use of the more highly effective agents hitherto known.

The oils which may be sulfonated to produce the addition agents used in compositions, baths, and processes of this invention are broadly classified as marine animal oils, and include fish oils, fish liver oils, and blubber oils. These oils are sulfonated, according to processes with which the art is already familiar, as by treating them with sulfuric acid under controlled conditions with respect to proportion of acid to oil, temperature, and time of treatment. The sulfonated oils are then washed with water to remove excess sulfuric acid and terminate the reaction.

In marine animal oils there is generally present a minor proportion of saturated oils, often called neutral or free oil, which is not readily sul fonated and remains in the sulfonated oil after the sulfonation and washing procedures have been completed. This neutral oil is sometimes objectionable in a plating composition and inv a preferred embodiment of this invention the sulfonated marine animal oil used as an addition agent is one from which neutral or free oil has been removed by extraction with an organic solvent such as ether, alcohol, or acetone.

The concentration of sulfonated marine animal oil employed in the cyanide-cadmium plating compositions, processes, and baths of this invention must be rather narrowly limited in order to produce the maximum beneficial effect. The

"concentration of sulfonated oil may advantageously be in the range of about from 0.1 to 3.0 grams per liter of bath, and it is particularly preferred to use a concentration of about from 0.3 to 1.6 grams per liter. If neutral oil is present in the addition agent it wil1 be understood that the weight proportion may be increased a proportionate amount. In dry or substantially solid plating compositions including-other bath constituents such as cyanide and cadmium, the sulfonated marine animal oil may be present in such proportion that when the entire composition is dissolved in water to make a bath of the desired cadmium and cyanide concentration for plating the concentration of sulfonated oil will be in the ranges above indicated.

'The cyanide-cadmium plating compositions and baths which are modified with a sulfonated marine animal oil according to this invention may be any cyanide-cadmium bath which upon electrolysis gives cathodic deposits of cadmium. Such compositions and baths necessarily contain a cyanide and a dissolved or bath-soluble cadmium compound. The cyanide may, for instance, be sodium or potassium cyanide and the cadmium compound may be a basic cadmium compound such as cadmium oxide, or both requirements may Example I Sodium cyanide 130 Cadmium oxide Nickel sulfate .5

The nickel sulfate was added as a metal addition agent and greatly magnified the effectiveness of the sulfonated oil.

Escample II V Sperm oil, obtained from the sperm whale, was sulfonated by reaction with of its weight of sulfuric acid (66 B.) at a temperature not exceeding 50 F. for 24 hours. The resulting product was found to be an effective addition agent for cyanide cadmium plating when used in the concentration of 0.5 gram per liter of the plating bath of the same composition as given in Example I. Deposits were bright and lustrous over a plating range of 5 to amp/sq. ft. and free from streaks or pits.

Example III Cod oil, the commercial oil obtained from the livers of cod fish, was sulfonated with 35% of its weight of sulfuric acid for 17 hours at a temperature not exceeding F. The resulting product was found to be an effective addition agent in a concentration of 0.7 gram per liter of the plating bath given in Example I. However, it was greatly improved in effectiveness by washing the sulfonated oil twice with twice its volume of water each time, the second time salting out the oil by sodium sulfate, then redissolving the acid-free oil in water in the amount of three times the volume .of oil, and stirring with ether in the amount of one and one-half times the volume of oil. The .ether layer containing the undesirable unsulfonated oil and stearine rising to the top was discarded, and the water solution of the sulionated oil was found to be an unusually effective addition agent for cyanide cadmium baths when used in the concentration of 3.2 grams per liter of the plating hath given in Example I above. This concentration of the 25% solution was equivalent to about 0.8 gram per liter of the undiluted sulfonated oil. Deposits were bright and uniform from 5 to amp/sq. ft. of current density, pitfree, smooth, and gave a high degree of uniformity in thickness of deposit when plating recessed articles.

7 Example IV .Seal oil, obtained from the blubber of the seal,

was sulfonated with 25% of its weight of sulfuric acid (66 B.) at a temperature of F. for 15 hours. The resulting product was an effective addition agent for cadmium plating, but was improved by extracting with ether as described in Example III above or with acetone. Deposits were bright and uniform from 7 to 45 amp/sq. ft. of current density.

Example V Shark liver oil was treated in the same manner as the cod oil described in Example III and was found to be a very effective addition agent for cyanide cadmium plating. Deposits were bright and lustrous from 10 to 40 amp/sq. ft.

While in the foregoing description certain specific compositions, baths, and processes have been shown to illustrate the invention, it will be understood that other compositions, baths, and processes may be employed within the spirit of the invention.

While I have disclosed specific cadmium baths heretofore, it will be understood that I do not intend to be limited thereby and that the teachings of my invention may be applied to cyanide cadmium baths generally.

I claim:

1. An aqueous cyanide-cadmium plating bath comprising from about 0.3 to 1.6 gram per liter of sulfonated cod oil.

2. An aqueous cyanide-cadmium plating bath comprising a small amount of nickel in the form of a salt soluble in aqueous cyanide solution and from about 0.3 to 1.6 gram per liter of sulfonated cod oil, the weight of sulfonated cod oil being about from one to two times the weight of nickel salt, calculated as nickel sulfate.

3. A dry cyanide-cadmium plating composition comprising a basic cadmium compound, and alkali metal cyanide, and sulfonated cod oil in such proportions that when the composition is dissolved in water at a concentration of cadmium and cyanide suitable as an electrodepositing bath the sulfonated cod oil will be present in a concentration of about from 0.3 to 1.6 grams per liter.

4. A dry cyanide-cadmium plating composition comp-rising a basic cadmium compound, an alkali metal cyanide, a minor proportion of nickel in the form of a salt soluble in aqueous cyanide solution, and sulfonated cod oil in such proportions that when the composition is dissolved in water at a concentration of cadmium and cyanide suitable as an electrodepositing bath the sulfonated cod oil will be present in a concentration of about from 0.3 to 1.6 grams per liter, the weight of sulfonated cod oil being about from one to two times the Weight of nickel salt, calculated as nickel sulfate.

' mium, the step comprising of electrodepositing cadmium from an aqueous cyanide-cadmium bath containing a small amount of nickel in the form of a bath soluble nickel salt, and sulfonated cod oil, the weight of sulfonated cod oil being about from one to two times the weight of nickel salt, calculated as nickel sulfate.

7. An aqueous cyanide-cadmium plating bath comprising from 0.3 to 1.6 gram per liter of sulfonated cod oil substantially free of neutral oil.

8. A dry cyanide-cadmium plating composition comprising a basic cadmium compound, an alkali metal cyanide, and sulfonatedcod oil substantially free of neutral oil, in such proportions that when the composition is dissolved in Water at a concentration of cadmium and cyanide suitable 5 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Camel Jan. 10, 1939 OTHER REFERENCES Number 10 Marine Animal Oils: Brocklesby; Bulletin LIX,

Fisheries Research Board of Canada, Ottawa, 1941, pp. 30, 31.

4 Transactions of the Electrochemical Society; vol. '78, pp. 345, 346. 

1. AN AQUEOUS CYANIDE-CADMIUM PLATING BATH COMPRISING FROM ABOUT 0.3 TO 1.6 GRAM PER LITER OF SULFONATED COD OIL. 